The present invention relates to vane assemblies for gas turbine engines.
A conventional multi-shaft gas turbine engine incorporates rotating, load-transmitting shafts which connect fans or compressors toward the upstream end of the engine, with turbines toward the downstream end of the engine. The fans, compressors and turbines are formed by rotating groups of blades through which the engine gases flow. Gas flow paths are conventionally controlled by placing fixed vanes, such as stator vanes and nozzle guide vanes, at various positions along the gas flow path, particularly at positions immediately upstream of compressors and turbines, in order to guide gases moving through the engine toward downstream components along desirable paths.
The vanes require cooling during engine operation and the present invention seeks to address this requirement.
The invention provides a vane assembly for a gas turbine engine, comprising a vane with an internal cavity, a cavity insert which, in use, is located within the cavity and adjacent the cavity wall to define therewith a path or paths for transpiration cooling across the wall surface, the cavity insert having an internal chamber to which cooling air is introduced, during use, and which has a plurality of exit openings to direct cooling air against the cavity wall for impingement cooling, and into the transpiration path, and the assembly further comprising at least one further cavity insert so shaped and positioned as to define with the cavity wall an extension to the or at least one of the transpiration paths.
The extension and the or a corresponding transpiration path preferably form a substantially continuous path. The extension path preferably extends from the downstream end of the or a transpiration path. The extension path preferably extends to a location at which cooling gas may vent from the vane.
Preferably the cavity insert and the further insert abut ribs formed along the cavity wall, to define at least one substantially wholly enclosed transpiration path and extension. Preferably the ribs extend in a chordal direction.
Preferably a plurality of extension paths are defined, each in communication with a respective transpiration path.
An attachment member, such as a flange, is preferably provided for attachment of the cavity insert to the vane, preferably by brazing, and preferably the flange closes off a transpiration path at an end of the vane to prevent egress of cooling air through the vane end. Preferably the vane is a nozzle guide vane.
In a second aspect, the invention provides a vane assembly comprising a vane with an internal cavity, a cavity insert which, in use, is located adjacent the cavity wall to define therewith a path or paths for transpiration cooling across the wall surface, the assembly further comprising an attachment member which bridges between the cavity wall and the cavity insert at or near one end of the vane to attach the cavity insert to the vane and to close the transpiration path at that end of the vane.
Preferably the attachment member is a flange, preferably carried by the cavity insert and preferably attached by brazing.
Preferably the cavity insert has an internal chamber to which cooling air is introduced, during use, and which has a plurality of exit openings to direct cooling air against the cavity wall for impingement cooling, and into the transpiration path, the assembly further comprising at least one further cavity insert so shaped and positioned as to define with the cavity wall an extension to the or at least one of the transpiration paths.
The extension and the or a corresponding transpiration path preferably form a substantially continuous path. The extension path preferably extends from the downstream end of the or a transpiration path. The extension path extends to a location at which cooling gas may vent from the vane.
Preferably the cavity insert and the further insert abut ribs formed along the cavity wall, to define at least one substantially wholly enclosed transpiration path and extension. Preferably the ribs extend in a chordal direction.
Preferably a plurality of extension paths are defined, each in communication with a respective transpiration path.
Preferably the vane is a nozzle guide vane.